Je. Morris et al., Clinical progression of transplanted large granular lymphocytic leukemia in Fischer 344 rats exposed to 60 Hz magnetic fields, BIOELECTROM, 20(1), 1999, pp. 48-56
The purpose of this study was to determine if 60 Hz magnetic fields can alt
er the clinical progression of leukemia in an animal model. Large granular
lymphocytic (LGL) leukemia cells from spleens of leukemic rats were transpl
anted into young male Fischer 344 rats, producing signs of leukemia in appr
oximately 2-3 months. The animals were randomly assigned to 4 treatment gro
ups (108/group) as follows: 1) 10 G (1.0 mT) linearly polarized 60 Hz magne
tic fields, 2) sham exposed [null energized unit with residual 20 mG (2 mu
T) fields], 3) ambient controls [<1 mG (0.1 mu T)1, and 4) positive control
s (a single 5 GL whole body exposure to Co-60 4 days prior to initiation of
exposure). All rats were injected intraperitoneally (ip) with 2.2 x 10(7)
LGL leukemic cells at the initiation of exposure or sham exposure. The magn
etic fields were activated for 20 h/day, 7 days/week, allowing time for ani
mal care. The experimental fields were in addition to natural ambient magne
tic fields. Eighteen rats from each treatment group were bled, killed, and
evaluated at 5, 6, 7, 8, 9, and 11 weeks of exposure. Peripheral blood hema
tological endpoints, changes in spleen growth, and LGL cell infiltration in
to the spleen and liver were measured to evaluate the leukemia progression.
No significant or consistent differences were detected between the magneti
c field exposed groups and the ambient control group, although the clinical
progress of leukemia was enhanced in the positive control animals. These d
ata indicate that exposure to sinusoidal, linearly polarized 60 Hz, 10 G ma
gnetic fields did not significantly alter the clinical progression of LGL l
eukemia. Furthermore, the data are in general agreement with previous resul
ts of a companion repeated-bleeding study in which animals were exposed for
18 weeks. (C) 1999 Wiley-Liss, Inc.